1. Field of Invention
The present invention relates generally to display or indicating devices, and more particularly to a novel display device and a combination of such devices wherein the solid color of a visually perceived area of each device is selectively changed by the relative movement between a planar, colored face and a highly reflective slotted plate.
2. Prior Art
Prior art optical display devices known to the Inventor comprise two general classes of construction. In one class, the displayed symbols emit light by operating in conjunction with separate illuminating sources and thereby distinguish the symbol from the background. A typical arrangement is one in which the characters or symbols are displayed in white on a dark background and thus provide the necessary contrast by which they are distinguished from the adjacent surroundings.
In the other class of display devices, no light is emitted from the display. Such devices typically comprise an array of display members which take the form of cylinders, discs, or other shapes, but each characterized by two visually distinguishable display surfaces. These prior art devices are generally exemplified by the devices shown in U.S. Pat. Nos. 3,140,553; 3,283,427; 3,295,238; 3,365,824; 3,303,494; and 3,624,941. The most common arrangement is to use rotating magnetized discs which turn as the polarity of an electromagnet is changed. U.S. Pat. No. 3,469,258 discloses the use of a reversibly magnetizable permanent magnet exterior to the magnetically actuable visual member which allows the exterior field to be switched by the use of a pulse in the energizing windings for the exterior magnet so that the remnant field thereby produced in the exterior magnet retains the magnetically actuable element in position without the necessity of a sustaining current.
A problem encountered using the rotating visual members with two distinct and contrastingly colored sides has been the generation of the initial torque necessary to rotate the visual member when the polarity of the electromagnet is reversed. Attempted solutions to this problem are exemplified by U.S. Pat. Nos. 3,295,238; 3,518,664; and 3,991,496.